where to inject b12 intramuscular How Give a Injection: Step-By-Step Instructions Safe B12 Injection Guide at
Description
The most common side effects of B12 injections are mild and temporary, including pain, redness, or swelling at the injection site, mild nausea or diarrhea, headache, dizziness, and itching near the injection area

I have literally not been the same since I took the vaccine
It suggests to me that you were given it when you didn't need it and if this is the case I'm not surprised at your skin's reaction

Gluten-free shouldnt be an issue
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